This invention relates to bag filling machines, and in particular to apparatus for topping-off a substantially filled bag with a final charge of particulate material to provide a predetermined, total weight charge in the bag.
In the course of filling particulate material into bags from a dispensing spout connected to a supply hopper, it is common practice to initially fill the bag in a bulk fill operation at a relatively high speed. A final charge of material is subsequently delivered into the bag to provide a total charge weight within a bag of particular volume or weight size. One such machine is of the vertical, bottom-fill auger type as disclosed in U.S. Pat. No. 5,109,894 issued to Harold R. McGregor, one of the named co-inventors on this application. As disclosed in that patent, the same, relatively high speed and relatively large diameter auger utilized for bulk feed of the initial charge of material into a bag is also utilized to top off the bag with a final charge of material. Load cells provided on the fill spout provide a reading of the initial weight charge delivered into the bag; and, thereafter, a computer or central processing unit (CPU) actuates the same fill auger at a slower speed, in response to a read-out of the initial weight charge, for a predetermined time or a predetermined number of revolutions of the auger to top off the bag.
Such a total fill system suffers from several problems. First of all, an undue time delay is caused by holding the same bag on the main filling spout while a single set of load cells record the initially filled weight of the bag, after which a computer receives and processes that filled weight data and thereafter actuates the bulk auger, at a slower speed, for a calculated number of revolutions to deliver the final charge into the bag. The total fill time is further extended by the time required to lift the vertical fill auger out of the material in the bag, and to thereafter lower the bag from the spout. Secondly, it is very difficult to obtain the required, precise control of the discharge of the slight amount of particulate material, e.g., one to three pounds, for accurately topping off the bag to the total, predetermined charge weight desired.
Machines for filling particulate material into bags in two stages are also known. Such machines dispense an initial, bulk charge of material into the bag at a relatively high speed, from a dispensing spout. The bag is then moved to a separate location where the final, small, top-off charge of material is added to the bag. However, such machines as presently known have several disadvantages. The load cell or weighing mechanism utilized at the top-off location is not sufficiently accurate; and, the total bag fill time is further extended by the use of a separate set of reforming devices to reform the bag top as it is moved to the top-off location.
With these disadvantages of bag filling and weighing apparatus in mind, an improved bag top-off and weighing apparatus has been developed which greatly reduces the total bag filling time while accomplishing the dispensing of the final, top-off charge of material into the bag with high precision and accuracy.